Community members demonstate after a vigil in memory of Alton Stering, who was shot dead by police, at the Triple S Food Mart in Baton Rouge, Louisiana, US, July 6, 2016. [Photo/Agencies]

BATON ROUGE - The US Justice Department said on Wednesday it would investigate the killing of a black man pinned to the ground and shot in the chest by two white police officers outside a convenience store in Baton Rouge, Louisiana.

Captured on at least two videos, graphic images of the shooting of Alton Sterling, 37, early Tuesday morning stirred protests and social media outcry over the latest case of alleged police brutality against African-Americans in cities from Ferguson, Missouri, to Baltimore and New York.

One of the two officers shot Sterling five times at close range, and the other removed something from Sterling's pants pocket as he was dying, according to images on a video recorded by Abdullah Muflahi, owner of the Triple S Food Mart where Sterling was killed in the parking lot.

"I'm heartbroken. It's outrageous. It's crazy," said Muflahi, who considered Sterling a friend and allowed him to sell CDs outside his store. He provided a copy of the video to Reuters and said police took a gun from Sterling's pocket.

Several hundred people gathered on Wednesday for a prayer vigil near the spot where Sterling was fatally shot, with speakers calling for peaceful protests, justice and unity in the face of "excessive force" by police against black residents.

Local officials rushed to defuse tensions, saying there would be an independent investigation, after media showed a separate graphic video of the shooting recorded by a bystander.

"I have very serious concerns. The video is disturbing, to say the least," Governor John Bel Edwards told reporters.

Baton Rouge Mayor-President Kip Holden and local police said they welcomed the probe launched by the Justice Department, the Federal Bureau of Investigation and federal prosecutors.

Presumptive Democratic presidential nominee Hillary Clinton said incidents like this one undermine trust between police and the communities they serve.

"Something is profoundly wrong when so many Americans have reason to believe that our country doesn't consider them as precious as others because of the color of their skin," she said in a statement.

There was no immediate statement on the incident from presumptive Republican nominee Donald Trump.